Reprogramming the immunosuppressive tumor microenvironment results in successful clearance of tumors resistant to radiation therapy and anti-PD-1/PD-L1.

Despite breakthroughs in immune checkpoint inhibitors (ICI), the majority of tumors, including those poorly infiltrated by CD8+ T cells or heavily infiltrated by immunosuppressive immune effector cells, are unlikely to result in clinically meaningful tumor responses. Radiation therapy (RT) has been combined with ICI to potentially overcome this resistance and improve response rates but reported clinical trial results have thus far been disappointing. Novel approaches are required to overcome this resistance and reprogram the immunosuppressive tumor microenvironment (TME) and address this major unmet clinical need. Using diverse preclinical tumor models of prostate and bladder cancer, including an autochthonous prostate tumor (Pten-/-/trp53-/-) that respond poorly to radiation therapy (RT) and anti-PD-L1 combinations, the key drivers of this resistance within the TME were profiled and used to develop rationalized combination therapies that simultaneously enhance activation of anti-cancer T cell responses and reprogram the immunosuppressive TME. The addition of anti-CD40mAb to RT resulted in an increase in IFN-y signaling, activation of Th-1 pathways with an increased infiltration of CD8+ T-cells and regulatory T-cells with associated activation of the CTLA-4 signaling pathway in the TME. Anti-CTLA-4mAb in combination with RT further reprogrammed the immunosuppressive TME, resulting in durable, long-term tumor control. Our data provide novel insights into the underlying mechanisms of the immunosuppressive TME that result in resistance to RT and anti-PD-1 inhibitors and inform therapeutic approaches to reprogramming the immune contexture in the TME to potentially improve tumor responses and clinical outcomes.

Progress and pitfalls with the use of image-guided personalised approaches in lymphoma.

The use of 18F-FDG PET CT has become an essential part of the management of patients with lymphoma. The last decade has seen unrivalled progress in research efforts to personalise treatment approaches using PET as a predictive imaging biomarker. Critical to this success has been the standardisation of PET methods and reporting, including the 5-point Deauville scale, which has enabled the delivery of robust clinical trial data to develop response-adapted treatment approaches.(1, 2) The utility of PET as a predictive imaging biomarker in assessing treatment success or failure has been investigated extensively in malignant lymphomas. Considerable progress has been made over the last decade, in using PET to direct more personalised "risk-adapted" approaches, as well as an increased understanding of some of the limitations. Arguably the greatest success has been in Hodgkin Lymphoma (HL) where PET was initially demonstrated to be a powerful predictive biomarker (3) and is now routinely used in both early-stage and advanced HL to reduce or escalate the use of chemotherapy as well as guiding the delivery of more selective radiotherapy to patients.

Reprogramming the tumour microenvironment by radiotherapy: implications for radiotherapy and immunotherapy combinations.

Radiotherapy (RT) is a highly effective anti-cancer therapy delivered to around 50-60% of patients. It is part of therapy for around 40% of cancer patients who are cured of their disease. Until recently, the focus of this anti-tumour efficacy has been on the direct tumour cytotoxicity and RT-induced DNA damage. Recently, the immunomodulatory effects of RT on the tumour microenvironment have increasingly been recognized. There is now intense interest in potentially using RT to induce an anti-tumour immune response, which has led to rethinking into how the efficacy of RT could be further enhanced. Following the breakthrough of immune check point inhibitors (ICIs), a new era of immuno-oncology (IO) agents has emerged and established immunotherapy as a routine part of cancer treatment. Despite ICI improving outcomes in many cancer types, overall durable responses occur in only a minority of patients. The immunostimulatory effects of RT make combinations with ICI attractive to potentially amplify anti-tumour immunity resulting in increased tumour responses and improved outcomes. In contrast, tumours with profoundly immunosuppressive tumour microenvironments, dominated by myeloid-derived cell populations, remain a greater clinical challenge and RT may potentially further enhance the immunosuppression. To harness the full potential of RT and IO agent combinations, further insights are required to enhance our understanding of the role these immunosuppressive myeloid populations play, how RT influences these populations and how they may be therapeutically manipulated in combination with RT to improve outcomes further. These are exciting times with increasing numbers of IO targets being discovered and IO agents undergoing clinical evaluation. Multidisciplinary research collaborations will be required to establish the optimal parameters for delivering RT (target volume, dose and fractionation) in combination with IO agents, including scheduling to achieve maximal therapeutic efficacy.

Involved Site Radiation Therapy in Adult Lymphomas: An Overview of International Lymphoma Radiation Oncology Group Guidelines.

Involved node radiation therapy for lymphoma was introduced with the aim of using the smallest effective treatment volume, individualized to the patient's disease distribution, to avoid the potentially unnecessary normal tissue exposure and toxicity risks associated with traditional involved field radiation therapy. The successful implementation of involved node radiation therapy requires optimal imaging and precise coregistration of baseline imaging with the radiation therapy planning computed tomography scan. Limitations of baseline imaging, changes in patient position, and anatomic changes after chemotherapy may make this difficult in routine practice. Involved site radiation therapy (ISRT) was introduced by the International Lymphoma Radiation Oncology Group as a slightly larger treated volume, intended to allow for commonly encountered uncertainties. In addition to imaging considerations, the optimal ISRT treatment volume also depends on disease histology, stage, nodal or extranodal location, and the type and efficacy of systemic therapy, which in turn influence the distribution of macroscopic and potential subclinical disease. This article presents a systematic overview of ISRT, updating key evidence and highlighting differences in the application of ISRT across the lymphoma clinical spectrum.

Novel Methods to Improve the Efficiency of Radioimmunotherapy for Non-Hodgkin Lymphoma.

Radioimmunotherapy (RIT) is a novel strategy for treating non-Hodgkin lymphoma (NHL). Several studies have shown the promising results of using RIT in NHL, which have led to FDA approval for two RIT agents in treating low grade NHL. In spite of these favorable results in low-grade NHL, most of the aggressive or relapsed/refractory NHL subjects experience relapses following RIT. Although more aggressive treatments such as myeloablative doses of RIT followed by stem cell transplantation appear to be able to provide a longer survival for some patients these approaches are associated with significant treatment-related adverse events and challenging to deliver in most centers. Therefore, it seems reasonable to develop treatment approaches that enhance the efficiency of RIT, while reducing its toxicity. In this paper, novel methods that improve the efficiency of RIT and reduce its toxicity through various mechanisms are reviewed. Further clinical development of these methods could expand the NHL patient groups eligible for receiving RIT, and even extend the use of RIT to new indications and disease groups in future.

Akt inhibition improves long-term tumour control following radiotherapy by altering the microenvironment.

Radiotherapy is an important anti-cancer treatment, but tumour recurrence remains a significant clinical problem. In an effort to improve outcomes further, targeted anti-cancer drugs are being tested in combination with radiotherapy. Here, we have studied the effects of Akt inhibition with AZD5363. AZD5363 administered as an adjuvant after radiotherapy to FaDu and PE/CA PJ34 tumours leads to long-term tumour control, which appears to be secondary to effects on the irradiated tumour microenvironment. AZD5363 reduces the downstream effectors VEGF and HIF-1α, but has no effect on tumour vascularity or oxygenation, or on tumour control, when administered prior to radiotherapy. In contrast, AZD5363 given after radiotherapy is associated with marked reductions in tumour vascular density, a decrease in the influx of CD11b+ myeloid cells and a failure of tumour regrowth. In addition, AZD5363 is shown to inhibit the proportion of proliferating tumour vascular endothelial cells in vivo, which may contribute to improved tumour control with adjuvant treatment. These new insights provide promise to improve outcomes with the addition of AZD5363 as an adjuvant therapy following radiotherapy.

Stereotactic ablative radiotherapy and immunotherapy combinations: turning the future into systemic therapy?

Radiotherapy (RT) is effective at cytoreducing tumours and until relatively recently the focus in radiobiology has been on the direct effects of RT on the tumour. Increasingly, however, the effect of RT on the tumour vasculature, tumour stroma and immune system are recognized as important to the overall outcome. RT is known to lead to the induction of immunogenic cell death (ICD), which can generate tumour-specific immunity. However, systemic immunity leading to "abscopal effects" resulting in tumour shrinkage outside of the RT treatment field is rare, which is thought to be caused by the immunosuppressive nature of the tumour microenvironment. Recent advances in understanding the nature of this immunosuppression and therapeutics targeting immune checkpoints such as programmed death 1 has led to durable clinical responses in a range of cancer types including malignant melanoma and non-small-cell lung cancer. The effects of RT dose and fraction on the generation of ICD and systemic immunity are largely unknown and are currently under investigation. Stereotactic ablative radiotherapy (SABR) provides an opportunity to deliver single or hypofractionated large doses of RT and potentially increase the amount of ICD and the generation of systemic immunity. Here, we review the interplay of RT and the tumour microenvironment and the rationale for combining SABR with immunomodulatory agents to generate systemic immunity and improve outcomes.

Short duration immunochemotherapy followed by radioimmunotherapy consolidation is effective and well tolerated in relapsed follicular lymphoma: 5-year results from a UK National Cancer Research Institute Lymphoma Group study.

UNLABELLED: We report a phase II study to evaluate the efficacy and toxicity of abbreviated immunochemotherapy followed by (90) Y Ibritumomab tiuxetan ((90) Y-IT) in patients with recurrent follicular lymphoma. Of the 52 patients enrolled, 50 were treated with three cycles of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisolone) or R-CVP (rituximab, cyclophosphamide, vincristine, prednisolone), followed by (90) Y-IT regimen (15 MBq/kg, maximum 1200 MBq) preceded by two infusions of 250 mg/m(2) rituximab. The overall response rate was 98% with complete response (CR) 30% and partial response (PR) 68%. 18 patients with a PR following chemotherapy improved to a CR following (90) Y-IT: a conversion rate of 40%. Seven patients with PR following (90) Y-IT subsequently improved to a CR 12-18 months later, leading to an overall CR rate of 44%. With a median follow-up of 5 years, median progression-free survival was 23·1 months and overall survival was 77·5% at 5 years. High trough serum rituximab levels (median 112 µg/ml; range 52-241) were attained after four doses of rituximab, prior to (90) Y-IT; this was not found to influence response rates. The treatment was well tolerated with few (13·5%) grade 3 or 4 infective episodes and manageable haematological toxicity. Abbreviated immunochemotherapy followed by (90) Y-IT is an effective and well-tolerated treatment in recurrent follicular lymphoma patients previously exposed to rituximab. TRIAL REGISTRATION: clinicaltrials.gov identifier: NCT00637832.

Acquired resistance to fractionated radiotherapy can be overcome by concurrent PD-L1 blockade.

Radiotherapy is a major part in the treatment of most common cancers, but many patients experience local recurrence with metastatic disease. In evaluating response biomarkers, we found that low doses of fractionated radiotherapy led to PD-L1 upregulation on tumor cells in a variety of syngeneic mouse models of cancer. Notably, fractionated radiotherapy delivered in combination with αPD-1 or αPD-L1 mAbs generated efficacious CD8(+) T-cell responses that improved local tumor control, long-term survival, and protection against tumor rechallenge. These favorable outcomes were associated with induction of a tumor antigen-specific memory immune response. Mechanistic investigations showed that IFNγ produced by CD8(+) T cells was responsible for mediating PD-L1 upregulation on tumor cells after delivery of fractionated radiotherapy. Scheduling of anti-PD-L1 mAb was important for therapeutic outcome, with concomitant but not sequential administration with fractionated radiotherapy required to improve survival. Taken together, our results reveal the mechanistic basis for an adaptive response by tumor cells that mediates resistance to fractionated radiotherapy and its treatment failure. With attention to scheduling, combination immunoradiotherapy with radiotherapy and PD-1/PD-L1 signaling blockade may offer an immediate strategy for clinical evaluation to improve treatment outcomes.

Consensus guidelines for the detection of immunogenic cell death.

Apoptotic cells have long been considered as intrinsically tolerogenic or unable to elicit immune responses specific for dead cell-associated antigens. However, multiple stimuli can trigger a functionally peculiar type of apoptotic demise that does not go unnoticed by the adaptive arm of the immune system, which we named "immunogenic cell death" (ICD). ICD is preceded or accompanied by the emission of a series of immunostimulatory damage-associated molecular patterns (DAMPs) in a precise spatiotemporal configuration. Several anticancer agents that have been successfully employed in the clinic for decades, including various chemotherapeutics and radiotherapy, can elicit ICD. Moreover, defects in the components that underlie the capacity of the immune system to perceive cell death as immunogenic negatively influence disease outcome among cancer patients treated with ICD inducers. Thus, ICD has profound clinical and therapeutic implications. Unfortunately, the gold-standard approach to detect ICD relies on vaccination experiments involving immunocompetent murine models and syngeneic cancer cells, an approach that is incompatible with large screening campaigns. Here, we outline strategies conceived to detect surrogate markers of ICD in vitro and to screen large chemical libraries for putative ICD inducers, based on a high-content, high-throughput platform that we recently developed. Such a platform allows for the detection of multiple DAMPs, like cell surface-exposed calreticulin, extracellular ATP and high mobility group box 1 (HMGB1), and/or the processes that underlie their emission, such as endoplasmic reticulum stress, autophagy and necrotic plasma membrane permeabilization. We surmise that this technology will facilitate the development of next-generation anticancer regimens, which kill malignant cells and simultaneously convert them into a cancer-specific therapeutic vaccine.

Fractionated 9°Y-ibritumomab tiuxetan radioimmunotherapy as an initial therapy of follicular lymphoma: an international phase II study in patients requiring treatment according to GELF/BNLI criteria.

PURPOSE: We report an international, multicenter phase II trial to evaluate the efficacy and toxicity of fractionated (90)Y-ibritumomab tiuxetan ((90)Y-IT) as initial therapy of follicular lymphoma (FL). PATIENTS AND METHODS: A total of 74 patients, with a median age of 61 years (range, 28 to 80 years), were recruited requiring initial therapy by Groupe d'Etude des Lymphomes Folliculaires (GELF)/British National Lymphoma Investigation (BNLI) criteria. Among them, 78% had stage III-IV disease, 32% intermediate, and 44% high-risk (according to FL International Prognostic Index). Treatment consisted of two doses of (90)Y-IT (11.1 MBq/kg) administered 8 to 12 weeks apart. Patients with more than 20% lymphoma infiltration of bone marrow (BM) received one infusion per week for 4 consecutive weeks of rituximab (375 mg/m(2)) and proceeded to fractionated radioimmunotherapy (RIT) only if a repeat BM biopsy demonstrated clearing of lymphoma to less than 20% involvement. The primary end point was end of treatment response of the intention-to-treat population. Secondary objectives were safety and progression-free survival (PFS). RESULTS: Initial overall response rate (ORR) was 94.4% (68 of 72 patients) with combined complete response (CR/CRu) of 58.3% (42 of 72 patients). Nine patients subsequently improved response making an ORR of 95.8% (69 of 72 patients) and CR/CRu of 69.4% (50 of 72 patients). At a median follow-up of 3.1 years (range, 0.2 to 5.2 years) estimated 3-year PFS is 58%, treatment-free survival 66%, and overall survival 95%. Median PFS is 40.2 months. Thirty patients have experienced disease progression and 24 have required further treatment. The treatment was well tolerated with few (2.8%) grade 3 or 4 infectious episodes or adverse events and manageable hematologic toxicity. CONCLUSION: Fractionated RIT using (90)Y-IT is an effective initial treatment for advanced-stage FL in patients with higher tumor burden requiring treatment.

Antibody-induced nonapoptotic cell death in human lymphoma and leukemia cells is mediated through a novel reactive oxygen species-dependent pathway.

Monoclonal antibodies (mAbs) have revolutionized the treatment of B-cell malignancies. Although Fc-dependent mechanisms of mAb-mediated tumor clearance have been extensively studied, the ability of mAbs to directly evoke programmed cell death (PCD) in the target cell and the underlying mechanisms involved remain under-investigated. We recently demonstrated that certain mAbs (type II anti-CD20 and anti-HLA DR mAbs) potently evoked PCD through an actin-dependent, lysosome-mediated process. Here, we reveal that the induction of PCD by these mAbs, including the type II anti-CD20 mAb GA101 (obinutuzumab), directly correlates with their ability to produce reactive oxygen species (ROS) in human B-lymphoma cell lines and primary B-cell chronic lymphocytic leukemia cells. ROS scavengers abrogated mAb-induced PCD indicating that ROS are required for the execution of cell death. ROS were generated downstream of mAb-induced actin cytoskeletal reorganization and lysosome membrane permeabilization. ROS production was independent of mitochondria and unaffected by BCL-2 overexpression. Instead, ROS generation was mediated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. These findings provide further insights into a previously unrecognized role for NADPH oxidase-derived ROS in mediating nonapoptotic PCD evoked by mAbs in B-cell malignancies. This newly characterized cell death pathway may potentially be exploited to eliminate malignant cells, which are refractory to conventional chemotherapy and immunotherapy.

Novel type II anti-CD20 monoclonal antibody (GA101) evokes homotypic adhesion and actin-dependent, lysosome-mediated cell death in B-cell malignancies.

The anti-CD20 mAb rituximab has substantially improved the clinical outcome of patients with a wide range of B-cell malignancies. However, many patients relapse or fail to respond to rituximab, and thus there is intense investigation into the development of novel anti-CD20 mAbs with improved therapeutic efficacy. Although Fc-FcγR interactions appear to underlie much of the therapeutic success with rituximab, certain type II anti-CD20 mAbs efficiently induce programmed cell death (PCD), whereas rituximab-like type I anti-CD20 mAbs do not. Here, we show that the humanized, glycoengineered anti-CD20 mAb GA101 and derivatives harboring non-glycoengineered Fc regions are type II mAb that trigger nonapoptotic PCD in a range of B-lymphoma cell lines and primary B-cell malignancies. We demonstrate that GA101-induced cell death is dependent on actin reorganization, can be abrogated by inhibitors of actin polymerization, and is independent of BCL-2 overexpression and caspase activation. GA101-induced PCD is executed by lysosomes which disperse their contents into the cytoplasm and surrounding environment. Taken together, these findings reveal that GA101 is able to potently elicit actin-dependent, lysosomal cell death, which may potentially lead to improved clearance of B-cell malignancies in vivo.

New antibody drug treatments for lymphoma.

INTRODUCTION: The advent of anti-CD20 monoclonal antibody (mAb) rituximab heralded a new era in the treatment of non-Hodgkin's lymphoma leading to significant improvements in outcome for patients. This unprecedented success has changed the mindset of the clinical community and catalyzed the interest in the pharmaceutical industry to develop the next-generation of antibodies and antibody conjugates in cancer. AREAS COVERED: There are an ever increasing number of newer generation anti-CD20 and rituximab 'bio-similars' undergoing early phase clinical development. In addition emerging novel therapies including antibody drug conjugates (brentuximab vedotin, SGN-35) and mAb against T-cell lymphomas antigens (e.g., zanolimumab) offer hope of improved outcome for other lymphomas. Bispecific T-cell-engaging antibodies and combination immunotherapy, also provide the promise of further improvements. Radiolabelled antibodies or radioimmunotherapy (RIT) has also demonstrated high clinical activity and two drugs namely 131I-tositumomab (Bexxar) and 90Y-ibritumomab (Zevalin) are licensed. EXPERT OPINION: Despite the large numbers of new anti-CD20 mAb currently undergoing clinical testing, improving on clinical efficacy of rituximab is a substantial challenge. Further improvements in outcome for patients will require rigorous testing in well designed clinical trials alongside the translation of new insights into mechanism of mAb action that lead to improvements in clinical efficacy.